Double-apron drafting mechanism



Oct. 11, 1960 w. KRAFT DOUBLE-APRON DRAFTING MECHANISM .Filed June 25, 1957 Mme-mm Uri/fer 440/2 1 drafting mechanism. In

2,955,330 DOUBLE-'APRON DRAFTING MECHANISM Walter Kraft, Stuttgart-Hofen, Germany, assignor to SKF Kugellagerfabriken Gesellschaft mit beschrankter Haftung, Schweinfurt, Germany, a German company Filed June 25, 1957, Ser. No. 667,781 Claims priority, application Germany June 25, 1956 1 'Claim. (Cl. 19-'-131) able to modify the drafting mechanism according to the length of fibre. This construction comprises two endless aprons which are situated one above the other and run over the driving pair of feed rollers where they form a nip for the fibres, shortly before the pair of delivery rollers, which likewise forms a rigid nip, the aprons run over what are known as tensioners which are carried by a cradle and by means of which a final compression point is formed between the aprons. In addition, this known construction has a guide plate for supporting the lower apron during the spinning of long fibres. If shorter fibres are to be spun, the guide plate is exchanged for a plate having an upwardly bent loop. This is adjustable in such a manner that the aprons are deflected and, as a result thereof, a kink is formed in the aprons and provides a further rigid nip. This plate is adjustable'accord- United States Patent ing to the fibre length so that the distance between two i of the nips can be varied. 7

It is an object of the present invention to provide an improved drafting mechanism for drafting textile fibres of different lengths.

In accordance with an aspect of this invention, a known drafting mechanism, having a main and a preliminary drafting zone, is converted into a single-zone drafting mechanism simply by the useof longer aprons which run over the driving pair of feed rollers, the middle rollers and the apron bars, while the middle pair of rollers can be adapted to act either to give a drafting nip or merely to control and guide the aprons.

Further, in accordance with this invention, provision is made for regulating the pressure of the middle top roller, so that, for drafting long fibres the pressure can be released and the middle top roller merely rests .With its own weight on the apron, or for drafting short fibres the required pressure can be adjusted in order to'obtain a nip at the middle pair of rollers. In order to regulate the pressure, a weighting spring is preferably provided which may convenientlybe brought into the operative or inoperative position by turning of an adjustment screw. The weighting spring may also be changed according to the pressure desired.

A further advantage of this invention consists in the fact that the distance between the middle rollers and the nips of the feed rollers and delivery rollers is variable so that adaptation to the particular length of fibre presents no' difiiculties. It is further convenient for the distance between the feed rollers and delivery rollers to nism having a main and I 11 and receive be adjustable so as to further extend the adjustment possibilities.

The above, and other objects, features and advantages of the-invention, will be apparent in the following detailed description of an illustrative embodiment thereof which is to be read in connection with the accompanying drawing forming a part hereof, and wherein:

Fig. 1 is a view of a known double-apron drafting mechanism, shown partly cut away,

and in section, and having a main and a preliminary drafting zone;

Fig. 2 is a view showing the drafting mechanism of Fig. I converted into a single-zone drafting mechanism in accordance with this invention; and

Fig. 3 is a detail view of part of the drafting mechanism shown in Fig. 2, but on a larger scale.

Referring to the drawing in detail, and initially to Fig. 1 thereof, it will be seen that a known drafting mechaa preliminary drafting zone by means of a bolt 3 and a 1 which extends through the whole machine. Mounted on the bracket 2, for pivoting upwards about a bolt 6, is a carrier arm 5 which consists of telescopic members of U-shaped cross-section and which can be locked, in the operating position, to the bracket 2, by a catch 7. Mounted for pivoting or swinging on the carrier arm 5 are guide arms 8, 9 and). The guide arms 8, 9 and 10 are loaded by helical springs the shafts of top rollers 15, 16 and 17 in holders 12, 13 and 14, respectively. Pivotally fixed to the middle holder 13 is a top apron cage 18 which serves to guide a top apron 19 and which includes an apron bar 181. The apron 19 runs upon the middle top roller 16. Bottom rollers 24, 25 and 26 are mounted for ro tation in brackets 21, 22 and 23, respectively, on the machine frame 20. The brackets 21, 22 and 23 are relatively adjustable in the direction longitudinally of the travel of the fibres being drafted. A bottom apron 27 runs upon the bottom middle roller 25 and over an apron bar 28, and is tensioned by a bar 29.

In accordance with the present invention, the known double-zone drafting mechanism described above with reference to Fig. 1, is converted, by minor reconstruction thereof, into a single-zone drafting mechanism capable of drafting fibres havinglengths up to the maximum distance between the rear feed rollers 15 and 24 and the front delivery rollers 17 and 26. a 6

Referring in detail to Fig. 2 of the drawing, wherein the unaltered parts of the converted mechanism are identified by the same reference numerals as were used in conincludes a bracket 2 fixed nut 4 to a supporting rod ing mechanism, it will be seen that, in the converted single-zone drafting mechanism, a long top apron 30 runs over the rear top feed roller 15, the middle top roller 16 and the apronbar 181 on the top apron cage 18, while a long bottom apron 31 runs over the rear bottom feed roller 24, the middle bottom roller 25 and the apron bar 28, and is tensioned by the bar 29. The weighting spring 11 associated with arm 9 may be removed so that the middle top roller 16 only rests, with its own weight, on the apron 30 and thus serves merely as a control or apron-guiding roller during the drafting of long fibres.

If short fibres are to be drafted, then the weighting spring 11 is re-installed so that a nip is formed at the middle pair of rollers 16 and 25. The draft is then effected only over the distance between the pair of middle rollers 16 and 25 and the pair of delivery rollers 17 and 26.

If predominantly long and medi -length fibres are to be drafted, then a long-staple cage may be substituted for the short-staple cage 18 illustrated in Figs. 1 and 2. As a result, the distance between the pair of middle rollers 16 and 25 and the pair of delivery rollers 17 and 26 will be increased. The telescoping construction of the carrier frame 5 and the adjustability of the bearings 21, 22 and 23 in the frame 20 permit this substitution of the cage. Long fibres will be drafted as described with reference to Fig. 2, that is, without the weighting spring 11, and with the top middle roller 16 merely serving as a control or apron-guiding roller. In order to draft medium-length fibres, the top middle roller 16 is weighted, by reinstalling the spring 11 associated with guide arm 9, so as to obtain 'a nip between rollers 16 and 25. The draft then takes place only between the pair of middle rollers 16 delivery rollers 17 and 26.

Preferably, in carrying out the present invention, the choice of apron lengths and the choice between a short staple cage and a long staple cage for any particular machine, are made in accordance with the character of the material which is to be drafted most often on that machine. Thus, for example, when the fibres range from the shortest to the longest, the arrangement with a shortstaple cage and an apron length which corresponds to the widest distance between the feed rollers and the delivery rollers is selected, but, when drafting fibres of medium and long length, a long-staple cage is used. These choices may however be varied.

Another way of relieving the pressure of the top middle roller, so that it is used only as a control roller, is to substitute a roller having a smaller diameter for it, while the spring 11 acting on arm 9 is retained. The guide arms 8, 9 and 10 are arranged so that they can swing down under the force of the weighting springs 11 only as far as a stop 60 and 60a, respectively, provided on the carrier arm 5. If the top middle roller 16 is removed, the holder 13 on the associated guide arm 9 will naturally come into a position closer to the plane of the drafting zone than when the original top middle roller of relatively large diameter is installed. Actually it will come into the position in which it rests against the stop on the carrier arm. In this position it can receive a top middle roller of smaller than usual diameter which will act simply as a control and apron guiding roller, because the force of the weighting spring will be taken up by the abutment of the middle guide arm 9 against the stop in the carrier arm and the top middle roller will thus not be weighted. However, if short fibres are to be drafted, then the small top roller is again exchanged for one of normal diameter so that the weighting spring can act on the guide arm 9 and a nip be formed at the middle pair of rollers 16 and 25.

Fig. 3 illustrates, by way of example, howthe pres sure of the spring 11 against the middle guide arm 9 may be varied. Screwed into the inner telescoping member 51 of the carrier arm, on which the guide arm 9 is mounted, is a set-screw 32 which carries a spring-retainer 33 at its lower end. By turning the set-screw 32, the pressure of the helical spring 11 on the middle guide arm 9 can be varied so that with high compression the spring 11, a nip is formed at the middle pair of rollers 16 and 25, but with moderate compression or complete release of the spring 11, the middle pair of rollers 16 and 25 act only as control and apron guiding rollers.

The setscrew 32 is secured against accidental turning and 25 and 'the 4 by a lock nut 34. In order to permit endwise displacement of the telescoping parts 51 and 52 of the carrier arm 5, slots 36 and 35 are provided in the outer carrier arm 5 and in the middle telescoping member 52 to receive the upper portion 'of the set-screw 32.

Although a particular embodiment of this invention has been described in detail herein with reference to the acover the distance I without departing from companying drawing, it is to be understood that the invention is not limited to that particular embodiment, or to the described modifications thereof, and that various changes and further modifications may be effected therein the scope or spirit of the invention,'except as defined in the appended claim.

What is claimed is:

A double-apron drafting mechanism for textile machines comprising a frame having bearings thereon rotatably supporting lower feed and delivery rollers and at least one lower middle roller disposed between said feed and delivery rollers, a carrier above said frame and carrying pivoted guide arms which rotatably support upper feed, delivery and middle rollers for movement toward and away from said lower feed, delivery and middle rollers, respectively, abutment means on said carrier for limiting pivotal movement of the guide arm carrying said upper middle roller in a direction toward said lower middle roller, said upper middle roller being replaceable by a middle roller of reduced diameter; an apron cage carried by the guide arm of said upper middle roller and defining an upper apron bar, a lower apron bar and tensioning bar, an upper apron running around said upper feed roller, tangentially over said upper middle roller, and around said upper apron bar, a lower apron running around said lower feed and delivery rollers and said lower apron bar and tensioning bar, means urging said upper feed and delivery rollers toward said lower feed and delivery rollers, respectively, to provide nips therebetween, and means for applying pressure to the guide arm of said upper middle roller to urge said upper middle roller toward said lower middle roller and thereby provide a nip between said middle rollers so that drafting of short fibres can occur between said middle and delivery rollers and so that, upon replacement of said middle roller by a middle roller of reduced diameter, the guide arm thereof abuts against said abutment means and said middle rollers act only to guide and control said upper and lower aprons and drafting of long fibres can occur between said feed and delivery rollers.

References Cited in the file of this patent UNITED STATES PATENTS 2,677,858 Kuehn et al. May 11, 1954 2,689,383 Burnham et al Sept. 21, 1954 2,751,632 Dausch June 26, 1956 2,756,462 Love et al. July 31, 1956 2,760,237 Spisak et al Aug. 28, 1956 FOREIGN PATENTS 718,926 Great Britain Nov. 24, 1954 745,127 Great Britain Feb. 22, 1956 880,385 France Dec. 28, 1942 

